The present invention relates to a view-finding optical system for use with single-lens reflex cameras, and more particularly, to a view-finding optical system capable of adjusting eyesight by moving part of the eyepiece along the optical axis of the finder.
Single-lens reflex cameras having a view-finding optical system capable of eyesight adjustment are available in various versions. Examples of such view-finding optical systems have been described in JPA-54-126530 (the term "JPA" as used herein means an "unexamined published Japanese patent application") and other patent applications.
However, JPA-54-126530 does not show an explicit example of a lens system that employs optical materials of low refractive indices and difficulty has been encountered in fabricating all-plastic lens components with a view to reducing the production cost. Further, the degree of eyesight adjustment that can be achieved by this lens system is only 3 diopters. This is not completely satisfactory in practical applications.